multiprotocol over atm (mpoa) - washington …jain/atm/ftp/atm_mpoa.pdfthe ohio state university raj...

Raj JainThe Ohio State University

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MPOAMPOAMultiprotocol Over ATMMultiprotocol Over ATM

Raj Jain

Professor of Computer and Information ScienceThe Ohio State University

Columbus, OH [email protected]

http://www.cis.ohio-state.edu/~jain/

Raj Jain

Horizontal small


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❑ RFC 1483

❑ Classical IP

❑ Next Hop Routing Protocol NHRP

❑ Multicast Address Servers MARS

❑ MPOA

❑ IP Switching

Overview


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Multiprotocol over ATM (MPOA)Multiprotocol over ATM (MPOA)❑ Problem: IP, IPX, DECnet routing, CLNP, AppleTalk DDP,

IPv6, Vines, etc over ATM

❑ Data transfer

❑ Address resolution

❑ Route determination

❑ Multicasting

❑ Multiple Server synchronization

❑ Solution: LAN emulation

❑ IP over ATM

❑ MPOA

❑ MPOA = LANE + IP over ATM + NHRP + MARS


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IP Over ATM: RFC 1483IP Over ATM: RFC 1483

❑ Hosts set up VCs with other hosts/routers on ATM

❑ PVC ⇒ No need to know ATM addresses

❑ Treat each VC as a separate wire

ATM Network


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Protocol MultiplexingProtocol Multiplexing1. LLC Encaptulation:

❑ Multiple protocols share the VC using LLC SNAP/SAP:

❑ Subnetwork Access Protocol/Service Access Point

❑ Routed Protocols:

❑ OUI = 00-00-00, EtherType = 08-00 ⇒ IP,

❑ Bridged Protocols:

❑ OUI = 00-80-C2 ⇒ 802.1

❑ Protocol ID = 0001 ⇒ 802.3/Ethernet w FCS0007 ⇒ 802.3/Ethernet w/o FCS

AA AA 03 00-00-00 08-00

DSAP SSAP Control OUI Prot. ID Payload


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2. VC Multiplexing:

❑ Set up individual VCs for each protocol

IP IPX

AAL5

IPIPX

AAL5VC 1

VC 2


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Classical IP Over ATMClassical IP Over ATM

❑ ATM similar to point-to-point WANs.Simpler than LAN emulation

❑ IP address: 123.145.134.65 ATM address:…1-614-999-2345-…

❑ Issue: IP Address ⇔ ATM Address translation

❑ Address Resolution Protocol (ARP)

❑ Inverse ATM ARP: VC ⇒ IP Address

❑ Solution: Logical IP Subnet (LIS) Server

❑ Ref: RFC 1577

Router

SW

Router

VC


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ARP over ATMARP over ATM❑ Address Resolution Protocol

❑ Logical IP Subnet (LIS) server responds to ARP

ATM Network

Router Router Router

HostHost

LISServer

LISServer

LISServer

LISServer


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NBMA ARP (NARP)NBMA ARP (NARP)❑ NBMA = Non-broadcast Multiple Access

❑ Examples: X.25, Frame-relay, SMDS, ATM

❑ Problem with RFC 1577 Approach: Data needs to gothrough routers even if on the same NBMA

❑ Like going to the airport just to go to next block

❑ Solution: ARP servers of different LIS's communicate

ATM Network HostHost

NARPServer

NARPServer

NARPServer

NARPServer


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❑ NARP servers cache the results

❑ NARP replies can be non-authoritative or authoritative

❑ NARP requests can be non-authoritative or authoritative

❑ Authoritative requests generally issued after failures.

❑ NARP works only if destination is on the same NBMA.

❑ NHRP, a superset of NARP, works even otherwise.


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NHRPNHRP❑ Next Hop Routing Protocol

❑ Developed by Routing over Large Clouds (ROLC) group

❑ Provides the next hop towards the destination.

❑ Next Hop Servers (NHSs)

NHRPClient

LocalCache

Query Cachemiss

NHRPServer

LocalCache

Query Cachemiss

NextServer


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❑ Hosts are configured with the address of local NHS

❑ NHRP servers cache the results

❑ NHRP replies can be non-authoritative or authoritative

❑ NHRP requests can be non-authoritative or authoritative

❑ Authoritative requests generally issued after failures.

❑ While waiting for NHRP shortcut, data may be forwardedalong the routed path.

❑ NHS learns about hosts via manual configuration orregistration


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NHRP FeaturesNHRP Features❑ Recording forward/reverse/both NHSs traversed

❑ Allows indicating QoS of path desired. Syntax TBD.

❑ Aggregated info: Range of addresses reachable via x usingprefix

❑ Cached information has an associated holding (expiry) time

❑ Purge request can be sent after a reconfiguration

❑ Allows authentication information in NHRP packets

❑ NHRP Domino effect = Every router on the path of a packetsends an NHRP request and forwards the packet withoutwaiting for the reply⇒ Only originating (not transit) routers should issue NHRPrequests


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IP AddressIP Address❑ Class A: Network Local0

71 24 bits

Network Local10142 16 bits

❑ Class B:

Network Local110213 8 bits

❑ Class C:

❑ Local = Subnet + Host (Variable length)

Router Router

Subnet

Host Group (Multicast)1110284 bits

❑ Class D:


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IP Multicast over ATMIP Multicast over ATM❑ Need to resolve IP multicast address to ATM address list

❑ Multicast Address Resolution Servers (MARS)

❑ Each MARS serves a cluster (LIS) of IP hosts

❑ Each LIS contains only one cluster

❑ Old LIS members not using MARS are not in the cluster

❑ Internet Group Multicast Protocol (IGMP)

❑ Hosts are configured with MARS address

❑ Multicast group members send IGMP join/leave messagesto MARS

Cluster members

LIS members


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❑ All cluster members join 224.0.0.1 (All local clustermembers)

❑ Hosts wishing to send a multicast send a resolution requestto MARS

❑ Senders do not need to be members of the multicast group

❑ IGMP queries to a multicast address can be used to get listof all members of the group

❑ Queries to 224.0.0.1 ⇒ "What are your multicast groupsand who are their members?"

❑ Responses are sent to respective group addresses so thatother members of the same group hear it and do notrespond.


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Multicast Data FlowMulticast Data Flow❑ Multicast Servers (MCS): Retransmit packets to multicast

members on a single point-to-multipoint VC (or multipleunicast VCs)

❑ VC Mesh

❑ Both models allowed. Each group can use different method.

❑ MARS keeps a point-to-multipoint VC with all clustermembers and a p-t-m VC with all MCSs

H1

MCS

H3

H2

H1 H3

H2


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❑ MARS broadcasts all join/leave messages to members sothat they can adjust their p-t-m VCs accordingly

❑ These messages have sequence numbers. Gap ⇒ Requestupdate from MARS.

❑ Clusters are connected via IP multicast routers

❑ Endpoints (e.g., IP multicast routers) may join all (orranges) of multicast groups

❑ Multiple backup MARSs allowed.

❑ If a group has both MCS and non-MCS members, MARSsupplies MCS as group list if asked by membersand member list if asked by MCS ⇒ Allows cluster members to send the packet only to MCS


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MPOA: OverviewMPOA: Overview❑ LANE hides QoS

❑ Both LANE and RFC 1577 need routers even in the sameATM network

❑ MPOA provides direct layer 3 connectivity across an ATMfabric

❑ For legacy hosts, MPOA provides direct layer 3connectivity to/from ATM-to-legacy bridges/routers⇒ Less Routers

ATM Network

BridgeRouter

Host


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❑ Layer 3 protocol runs directly over ATM ⇒ Can use ATMQoS

❑ LANE operates at layer 2

❑ RFC 1577 operates at layer 3

❑ MPOA operates at both layer 2 and layer 3 ⇒ MPOA can handle non-routable as well as routableprotocols

❑ MPOA uses LANE for its layer 2 forwarding

❑ MPOA = Unified approach for all layer 3 protocols overATM

❑ MPOA servers can be replicated. Clients are not aware ofreplication.


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MPOA Reference ModelMPOA Reference Model

ATM Network

Edge Device

IASGCoordination

RouteServer

DefaultForwarder

RemoteForwarder

ATMHost

ATMHost

Edge Device

Legacy Host Legacy Host


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MPOA ComponentsMPOA Components❑ Internet Address Sub-Group (IASG)

≈ Subnet ≈ LIS ≈ Cluster

❑ IASG Coordination functions (ICFG)≈ LIS Server: Host registration, etc.

❑ Internet Broadcast Sub-Group (IBSG) ≈ Cluster

❑ Route Servers = Run routing protocols and determine routes(does not forward packets)

❑ Edge Devices = ATM to legacy bridge/router

❑ Multicast Servers: Layer 3 multicast within an IASG

❑ Default Forwarders: For intra-IASG traffic in the absence ofdirect client-to-client connectivity. Also acts as multicastserver.


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❑ Remote Forwarder: Between IASG's

❑ MPOA Client = ATM-attached Host (AHFG) or Edgedevice (EDFG)

❑ MPOA Server = IASG CF (ICFG), Route Server (RSFG),or Intra-IASG broadcast/unknown server (IBUFG)


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MPOA ArchitectureMPOA Architecture

LANE

Edge Device

IASGCoordination

RouteServer

DefaultForwarder

RemoteForwarder

MPOAHost

LANEHost

Edge Device

Legacy Host Legacy Host

LANE Clients


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ICFGICFG❑ IASG Coordination Functional Group

❑ Coordinates IASG distributed over multiple legacy LANsand ATM stations

❑ For example, a single IPv4 subnet across multiple Ethernets

❑ Hosts find IASG CF's address from configuration server

❑ Hosts register protocols and addresses with ICFG

❑ LANE may be used to reach hosts on the same IASG

❑ IASG is layer-3 protocol specific

❑ If a host operates two layer-3 protocols, it is a member oftwo IASG's


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Route ServersRoute Servers❑ Legacy router = Route server + packet forwarder

❑ Route server functions exchanges connectivity informationand determines route

❑ Packet forwarding function forwards packets in the rightdirection

❑ In an ATM-to-ATM router, packet reassembly andforwarding can be avoided.

❑ Only route server function is needed.

❑ Packet forwarding is needed only in edge devices


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❑ Virtual Routers = Route servers and packet forwarders indifferent boxes

❑ Conventional Routers =Route servers and packet forwardersin one physical device


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Address ResolutionAddress Resolution❑ Hosts:

❑ Host queries IASG CF about a layer 3 address

❑ ICFG responds with the ATM address

❑ ICFG may send the query to route server

❑ Route servers use NHRP to determine the next-hop

❑ Edge Devices: If the destination is

❑ A legacy host behind another edge device, it forwardsthe ARP to that device

❑ An ATM host, it may answer ARP for the host.

❑ Unknown, it broadcasts the ARP on ELAN.


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Data FlowData Flow❑ Default flow:

❑ Used when short cut does not exist.

❑ AHFG sends to Remote forwarder or default forwarder

❑ Edge devices use LANE for delivery based on MACaddresses

❑ Dual-mode hosts use LANE for intra-IASG traffic anduse AHFG for inter-IASG traffic

❑ Default forwarder will send to remote forwarder ifnecessary

❑ Shortcut Flow:

❑ Send directly on a VC to the destination or edge device


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Protocol StackProtocol Stack

Multicast Address Resolution

Next Hop Address Resolution

LAN Emulation

Multiprotocol Over ATM

Routing

Bridging


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IP SwitchingIP Switching❑ Normally the packets are reassembled and forwarded in the

router. Segmentation and reassembly in the forwarder.

❑ If a flow is deemed to be "flow oriented", previous node istold to set up a new VC. Forwarder uses cached info.

ATMSwitch

PacketForwarder

Node Node

IP Switch

Default

ATMSwitch

PacketForwarder

Node Node

IP Switch

1st hoplabeled


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❑ Downstream nodes may also ask for a new VC.The switch then makes a mapping for cut-through

❑ Flow-oriented traffic: FTP, Telnet, HTTP, Multimedia

❑ Short-lived Traffic: DNS query, SMTP, NTP, SNMP,request-response

❑ Ipsilon claims that 80% of packets and 90% of bytes areflow-oriented.

ATMSwitch

PacketForwarder

Node Node

IP SwitchCut-throughComplete

ATMSwitch

PacketForwarder

Node Node

IP Switch

2nd hoplabeled


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IP Switch Protocol StackIP Switch Protocol Stack❑ Generic Switch Management Protocol (GSMP)

❑ Controls the ATM Switch Engine

❑ Set up, tear down VCs

❑ Ipsilon Flow Management Protocol (IFMP)

❑ Enables communication between nodes/switches

❑ Associates flows with VCs

❑ Defines flow redirect messages and acks

❑ Implemented in ATM end stations and edge routers

❑ Implemented as a software layer over an ATM switch

❑ Ipsilon claims GSMP to be 2000 lines,IFMP 10000 lines of code


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SummarySummary

❑ Classical IP allows ARP using LIS servers

❑ NHRP allows shortcut between ATM hosts and edge devices

❑ MARS allows multicast

❑ MPOA combines LANE, NHRP, and MARS

❑ IP switching selectively changes some flows to switched path


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References: IP over ATMReferences: IP over ATM❑ RFC 1483, "Multiprotocol Encaptulation over ATM

Adaptation Layer 5," July 1993.

❑ RFC 1735, "NBMA Address Resolution Protocol (NARP)",December 1994

❑ D. Katz, "NBMA Next Hop Resolution Protocol (NHRP),"Internet Draft, December 1995.

❑ G. Armitage, "Support for Multicast Over UNI 3.0/3.1based ATM Networks," Internet Draft, February 1996.

❑ RFC 1755, "ATM Signaling support for IP over ATM,"February 1995

❑ RFC 1932, "IP Over ATM: A Framework Document," April1996


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❑ RFC 1926, "An Experimental Encapsulation of IPDatagrams on Top Of ATM," April 1996

❑ RFC 1821, "Integration of Real-time Services in an IP-ATMNetwork Architecture," August 1995

❑ RFC 1680, "IPng Support for ATM Services," August 1994.

❑ RFC 1626, "Default IP MTU for use over ATM AAL5,"May 1994.


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References: MPOAReferences: MPOA❑ G. Armitage, "Multicast and Multiprotocol Support for

ATM Based Internets," Computer Communications Review,April 1995(?)

❑ C. Brown, "Baseline text for MPOA," ATMF/95-0824R6,February 26, 1996.


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References: IP SwitchingReferences: IP Switching❑ Ipsilon, "IP Switching: The intelligence of Routing, the

Performance of Switching," February 1996.

❑ P. Newman, et al, "Flow Labeled IP: Connectionless ATMunder IP," Networld+Interop, April 1996.

❑ RFC 1953, "Ipsilon Flow Management ProtocolSpecification for IPv4, Version 1.0," May 1996.

❑ RFC 1954, "Transmission of Flow Labeled IPv4 on ATMData Links, Ipsilon Version 1.0," May 1996.


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QuizQuizT F Please check True/False

1. o o MPOA reduces the number of routers required in a network.

2. o o MARS is a satellite-based long distance communicationmethod

3. o o NHRP allows a shortcut path between two ATM devices ondifferent subnets.

4. o o VC multiplexing means several applications sharing a VC.

5. o o NHRP gives authoritative answers only if requested so.

6. o o VC mesh among n nodes requires n2 VCs.

7. o o Edge devices connect ATM network to legacy networks.

8. o o IP switch switches all IP packets.

9. o o With MPOA, you do not LANE.

10. o o MPOA supports IPX.

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